The logic of using the lefter lanes to pass, while using the rightmost lanes for merging, trucks, and slow cars… makes the left lanes de facto “fast lanes”. The #4 lane being the merging/trucks area and the #3 lane for slower-traffic and “posted limit” afficianados. The #2 lane for going 70 to 75, and the #1 lane for everything above.
And if everyone followed that common courtesty (and there’s no logical reason not to), you’d have far less cars bunching up, less cars traveling in wolfpacks, and less cars being pointlessly stuck in between other cars driving at parallel speeds.
The prevalence of slower drivers on the left side is a greater danger than the danger posed by general speeders.
But yes, the carpool lane is of course mainly for carpoolers and motorcyclists and emergency vehicles, that was their intended original purpose. The “slow stay right” rule (in some areas a law, other areas just a social courtesy) definitely applies on the normal freeway at all times. Without it, there’d be far more chaos.
The problem with carpool lanes, is often there is just one of them per freeway, making passing slow people impossible if one is on them. And it all begs the original question of why slow drivers would ever want to be in a lane where they cause pointless distress to others, when those slower drivers would be perfectly fine driving in the #3 or #4 lane of the normal freeway, and at the exact same speed personal preferred speed they were using in the carpool lane, and they’d be in flow of the road, rather than being a pointless obstacle. Only self-centeredness and a clingy emotional placement of one single law “the posted speed limit” over actual reality and safety… causes people to drive slow in the leftside lanes for no reason beyond the fact that they “feel like it”. I’m generalizing, and there’s exceptions occasionally due to the dynamics of the road. Some speeders are indeed too fast to be safe. And some slow left lane drivers are only over there temporarily and they get hassled way too soon by selfish people behind them before they move over. But if they never move over, even when a clearing in traffic occurs… then it is they who are selfish.